[LLVMbugs] [Bug 18596] New: clang (from 3.2 to the current trunk) hangs on valid code at -Os and above on x86_64-linux-gnu

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18596

            Bug ID: 18596
           Summary: clang (from 3.2 to the current trunk) hangs on valid
                    code at -Os and above on x86_64-linux-gnu
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following testcase causes the current clang trunk (as well as 3.2 to 3.4)
to hang when compiling at -Os and above in both 32-bit and 64-bit mode on
x86_64-linux-gnu.

This is a regression from clang 3.1. 

$ clang-trunk -v
clang version 3.5 (trunk 199196)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.3
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
$ 
$ clang-trunk -O1 small.c; a.out
$ clang-3.1 -Os small.c; a.out
$ 
$ timeout -s 9 30 clang-trunk -Os small.c
Killed
$ timeout -s 9 30 clang-3.4 -Os small.c
Killed
$ timeout -s 9 30 clang-3.3 -Os small.c
Killed
$ timeout -s 9 30 clang-3.2 -Os small.c
Killed
$ 
$ 


-----------------------------------------


int a, b, c, e[1], f, g, h, i, k, m, n;
short j;

struct
{
  short f1;
} d;

static int
fn1 (int p1)
{
  int l = 64696;
  for (f = 0; f != 1; f--)
    {
      if (d.f1 > l)
    {
      h = p1;
      if (!h)
        l = 0;
    }
      else
    return b;
      for (; a; a++)
    if (e[a])
      break;
    }
  for (; p1; p1++)
    {
      if (h)
    continue;
      if (l)
    i = j = k = g && d.f1 != p1;
      for (; h != 1; h++)
    ;
    }
  return 0;
}

int
main ()
{
  m = c = 1;
  n = fn1 (c);
  return 0;
}

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